General Statistics

Question 1

Population definition

Answer 1

The whole set of items that are of interest

Question 2

Census definition

Answer 2

An observation or measurement of every member of a population

Question 3

Sample definition

Answer 3

A selection of observations taken from a subset of the population which is used to find out information about the population as a whole

Question 4

Census advantages

Answer 4

It should give a completely accurate result

Question 5

Census disadvantage

Answer 5

• Time consuming and expensive
• Cannot be used when the testing process destroys the item
• Hard to process large quantity of data

Question 6

Sample advantages

Answer 6

• Less time consuming and expensive than a census
• Fewer people have to respond
• Less data to process than in a census

Question 7

Sample disadvantages

Answer 7

• The data may not be as accurate

- The sample may not be large enough to give information about small sub-groups of the population

Question 8

How to increase the accuracy of a sample

Answer 8

Increase the number of size of the sample - especially if the population is varied (more variety needs a larger sample)

Question 9

Sampling units definition

Answer 9

Individual units of a population

Question 10

Sampling frame definition

Answer 10

A numbered/named list of sampling units

Question 11

Simple random sampling definition

Answer 11

A sampling system whereby each sampling unit has an equal chance of being selected

Question 12

Two methods of choosing sampling units in a simple random sample

Answer 12

Random number generation and lottery

Question 13

Lottery sampling definition

Answer 13

Randomly picking out certain names (e.g. names in a hat)

Question 14

Systematic sampling definition

Answer 14

Choosing the required sampling units at regular intervals from an ordered sampling frame - the first sampling unit should be selected at random within the first interval, and then it is continued from them

Question 15

Stratified sampling definition

Answer 15

Dividing the population into mutually exclusive strata (e.g. male/female) and a proportional random sample is taken from both

Question 16

Advantages of simple random sampling

Answer 16

• Free of bias
• Easy and cheap to implement for small samples
• Each sampling unit has a known and equal chance of prediction

Question 17

Disadvantages of simple random sampling

Answer 17

• Not suitable when the population size or sampling size is large
• Requires a sampling frame

Question 18

Advantages of systematic sampling

Answer 18

• Simple and quick to use

- Suitable for large samples and large populations

Question 19

Disadvantages of systematic sampling

Answer 19

• Requires a sampling frame

- Can introduce bias if sampling frame is not random

Question 20

Quota sampling definition

Answer 20

Selecting a sample that reflects the characteristics as a whole by dividing the populations into groups based on a given characteristic then allocate each individual in a group into an appropriate quote

Question 21

Opportunity sampling definition

Answer 21

Taking the sample from people who are available at the time the study is performed assuming they fulfil the criteria

Question 22

Advantages of quota sampling

Answer 22

• Allows a small sample to be representative of the population
• No sampling frame is required
• Quick, easy and inexpensive
• Allows for easy comparison between different groups within a population

Question 23

Disadvantages of quota sampling

Answer 23

• Non-random sampling can introduce bias
• Population must be divided into groups which can be costly or inaccurate
• Increasing scope of study increases number of groups, which adds time and expense
• Non-responses are ignored rather than recorded as such

Question 24

Advantages of opportunity sampling

Answer 24

• Easy to carry out

- Inexpensive

Question 25

Disadvantages of opportunity sampling

Answer 25

• Unlikely to provide a representative sample

- Highly dependent on individual researcher

Question 26

Quantitative data/variable definition

Answer 26

Data/variables associated with numerical observations

Question 27

Qualitative data/variable definition

Answer 27

Data/variables associated with non-numerical observations

Question 28

Continuous variable definition

Answer 28

Variables that can take any value in a given range

Question 29

Discrete variable definition

Answer 29

Variables that can only take specific values in a given range

Question 30

Daily mean temperature definition and unit

Answer 30

The average hourly temperature during a 24-hour period (°C)

Question 31

Daily total rainfall

Answer 31

The total rainfall (including solid precipitation - which is melted then measured), amounts less than 0.05mm are recorded as trace (mm)

Question 32

Daily total sunshine

Answer 32

Total time of sunshine, recorded to the nearest 1/10 of an hour (hr)

Question 33

Daily mean wind direction and windspeed

Answer 33

Average windspeed over 24 hours from midnight to midnight, directions are given as bearings and cardinal directions. Categorised according to the Beaufort scale. (kn)

Question 34

Conversion of knots to mph

Answer 34

1 kn = 1.15 mph

Question 35

Daily maximum gust

Answer 35

Highest instantaneous windspeed and direction (kn)

Question 36

Daily maximum relative humidity

Answer 36

The percentage of air saturation with water vapour - humidities over 95% give rise to misty and foggy conditions (%)

Question 37

Daily mean cloud cover

Answer 37

Average cloud cover (oktas - eighths of the sky)

Question 38

Daily mean visibility

Answer 38

The greatest horizontal distance at which an object can be seen in daylight (Dm)

Question 39

Daily mean pressure

Answer 39

Average pressure (hPa - hectopascals)

Question 40

Years of recordings

Answer 40

1987 and 2015

Question 41

Months of recordings

Answer 41

May to October